Investigation of congenital and acquired hemorrhagic and thrombotic disorders in man to elucidate the clinical entities and to investigate the molecular basis for the defects. This has involved purification of coagulation proteins, immunologic investigation of coagulation proteins and inhibitors, and defining the role of these proteins in normal hemostasis and abnormal hemostasis. BIBLIOGRAPHIC REFERENCE: Greipp, P. and Gralnick, H.: Platelet to Leukocyte Adherence Phenomena Associated with Thrombocytopenia. Blood 47: 513, 1976.